I use AddThis dashboard to check the data on how my blog has been shared across social bookmarking sites. And as I use AddThis widget to show Google +1 button on my blog posts, I can also get the sharing trend of Google +1 button from my blog pages. But just a day or two ago Google +1 Metrics has been added in Google Webmaster Tools. Now if you open your site dashboard from Webmaster Tools, you will see +1 Metrics Menu at the sidebar. Click on it to get all the sub-menus and explore all the detailed info including how many unique visitors clicked Google +1 button on your site and which pages have been shared and when. There is another interesting aspect of measuring the search impact of Google +1 button on your site. As you can see from the screenshot, you will find the number of +1 annotated impressions on Google search results page compared to the total impressions for your site. You can get the same data on actual results page clicks on your site link. And if you generate enough traffic to gain a substantial data, Google will show the difference on CTR for pages shown from with & without + annotated results.
So there are lots of extra things from AddThis analytics. AddThis analytics is quite good. But if you want to get a bit of more information like how effective your ads are, you might want to take a peek at Google Webmaster Tools dashboard. Google is sharing their own data on their own social button after all